Neural crest-derived, mesenchymal, fibroblastic cell populations differentiate into distinct cell-types in the eye, including corneal nerves, corneal endothelium, stromal keratocytes, non-myelinating and myelinating Schwann cells, connective tissues of limbus, conjunctiva, choroid, sclera, eyelids, iris, lacrimal and other glands, and in birds, scleral ossicles. Each tissue forms a unique extracellular matrix (ECM) that changes with developmental age. Immunocytochemistry, in situ hybridization, mass spectrometry, surface plasmon resonance spectrometry, knock-down and mis-expression analysis, ability to construct chick-quail chimeric embryos, and laser- assisted microdissection (LMD) now allow examination and manipulation of differentiation in small groups of cells in different parts of the eye to better assess signals regulating cell and nerve growth cone migrations and differentiation. Hypothesis: highly charged ECMs unique to each site, bind and release growth-, differentiation-, neurotropic-, and neurotrophic-factors that determine corneal transparency and innervation, and normal functions of other tissues. Aim 1: Determine carbohydrate structures and bound factors in key locations of embryonic eyes. Mass spectrometry will identify and quantitate specific glycosaminoglycans present in ECMs and details of their structures, including structural positions of sulfate groups and identification of sialic acid types. Aim 2: Determine the mechanism of each step in corneal sensory innervation by neural crest-derived growth cones of trigeminal ganglion neurons. Aim 3: Determine the normal lineage sources of non-myelinating Schwann cells of corneal stroma during development; identify marker proteins expressed by these cells and effects on their differentiation from perturbing ECM synthesis. Significance: Extent to which human corneas heal and become re-innervated after LASEK, LASIK, PRK or transplantation is determined by signals residing in participating ECMs, particularly in their posttranslational modifications. Although transplanted corneas generally remain transparent, re-innervation of the graft is very slow (years) and often incomplete, depriving patients of corneal touch sensitivity and blink reflex. Research proposed here will elucidate relationships between proteoglycan forms and distributions, and paths chosen by corneal nerves and non-myelinating Schwann cells during innervation of embryonic corneas. These data will facilitate designing strategies to better reinnervate transplanted or modified adult corneas.